Power supply connection for monolithic print heads
Large print heads with many thousands of nozzles may have current consumption in excess of 20 Amperes. This would cause significant problems if standard interconnection techniques were used. The present invention effects very high current delivery to print heads by utilizing the entire long edges of the print head as power terminals.The V+ and V- connections are fabricated as 200 .mu.m wide strips of 1 .mu.m aluminum along the edges of the chip which are perpendicular to the print direction. Lines of aluminum extend from the V.sup.+ connection until the row of nozzles closest to the V.sup.- connection. These lines pass between every second nozzle, and are as wide as the device layout and process technology will allow. Lines of aluminum extend from the V.sup.- connection until the row of nozzles closest to the V.sup.+ connection. These lines are interdigitated with the V.sup.+ lines. This power supply configuration allows tens of amperes to be supplied to print heads with very low electrical resistance and without significant temperature rise in the on-chip connections. Also, electromigration is sufficiently low that it is not a significant factor in device reliability.
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Claims
1. A drop on demand print head comprising a plurality of electrothermal heater elements formed on a silicon chip and electrical power connections for supplying power to said electrothermal elements, the improvement wherein said connections are formed on the chip surface substantially at opposite edges of the print head and extend a distance substantially equal to the length of the corresponding edge.
2. The invention defined in claim 1 wherein said connections are adapted to conduct current in excess of 20 Amperes.
3. The invention defined in claim 1 wherein said connections have a width equal to or greater than approximately 200.mu.m.
4. The invention defined in claim 1 wherein said connections have a thickness of approximately 1.mu.m.
5. The invention defined in claim 1 wherein said connections are generally perpendicular to the print feed direction of said print head.
6. The invention defined in claim 1 further comprising a main connection from the electrical power circuits on said chip surface to an external circuit, said main connection being characterized by the region of contact to said chip electrical power circuits being situated in a recess formed in the substrate of said chip.
7. The invention defined in claim 6 wherein said recess is formed to a depth which is in excess of 10.mu.m, and is less than the thickness of said substrate.
8. The invention defined in claim 6 wherein said recess is formed to a depth so that the tops of said main electrical connection do not protrude beyond the surface of said chip electrical power circuits.
9. The invention defined in claim 1 wherein said print head comprises:
- (a) a plurality of drop-emitter nozzles;
- (b) a body of ink associated with said nozzles, said body of ink forming a meniscus with an air/ink interface at each nozzle;
- (c) drop selection apparatus operable upon the air/ink interface to select predetermined nozzles and to generate a difference in meniscus position between ink in selected and non-selected nozzles; and
- (d) drop separation apparatus adapted to cause ink from selected nozzles to separate as drops from the body of ink, while allowing ink to be retained in non-selected nozzles, said drop selection apparatus being capable of producing said difference in meniscus position in the absence of said drop separation apparatus.
10. The invention defined in claim 1 wherein said print head comprises:
- (a) a plurality of drop-emitter nozzles;
- (b) a body of ink associated with said nozzles, said body of ink forming a meniscus with an air/ink interface at each nozzle and said ink exhibiting a surface tension decrease of at least 10 mN/m over a 30.degree. C. temperature range;
- (c) drop selection apparatus operable upon the air/ink interface to select predetermined nozzles and to generate a difference in meniscus position between ink in selected and non-selected nozzles; and
- (d) drop separation apparatus adapted to cause ink from selected nozzles to separate as drops from the body of ink, while allowing ink to be retained in non-selected nozzles.
11. The invention defined in claim 1 wherein said print head comprises:
- (a) a plurality of drop-emitter nozzles;
- (b) a body of ink associated with said nozzles;
- (c) a pressurizing device adapted to subject ink in said body of ink to a pressure of at least 2% above ambient pressure, at least during drop selection and separation to form a meniscus with an air/ink interface;
- (d) drop selection apparatus operable upon the air/ink interface to select predetermined nozzles and to generate a difference in meniscus position between ink in selected and non-selected nozzles; and
- (e) drop separation apparatus adapted to cause ink from selected nozzles to separate as drops from the body of ink, while allowing ink to be retained in non-selected nozzles.
12. In a drop on demand print head comprising a plurality of integrated circuits formed on a silicon substrate, an arrangement of an electrical connection from said integrated circuits to an external circuit, said arrangement being characterized by the region of contact to said integrated circuits being situated in a bevel formed in the substrate of said integrated circuits.
13. The invention defined in claim 12 wherein said bevel is formed to a depth so that the tops of said electrical connections do not protrude beyond the surface of said integrated circuit, said surface being the surface in which said bevel is formed.
14. The invention defined in claim 12 wherein said print head comprises:
- (a) a plurality of drop-emitter nozzles;
- (b) a body of ink associated with said nozzles;
- (c) a pressurizing device adapted to subject ink in said body of ink to a pressure of at least 2% above ambient pressure, at least during drop selection and separation to form a meniscus with an air/ink interface;
- (d) drop selection apparatus operable upon the air/ink interface to select predetermined nozzles and to generate a difference in meniscus position between ink in selected and non-selected nozzles; and
- (e) drop separation apparatus adapted to cause ink from selected nozzles to separate as drops from the body of ink, while allowing ink to be retained in non-selected nozzles.
15. The invention defined in claim 12 wherein said print head comprises:
- (a) a plurality of drop-emitter nozzles;
- (b) a body of ink associated with said nozzles said body of ink forming a meniscus with an air/ink-interface at each nozzle;
- (c) drop selection apparatus operable upon the air/ink interface to select predetermined nozzles and to generate a difference in meniscus position between ink in selected and non-selected nozzles; and
- (d) drop separation apparatus adapted to cause ink from selected nozzles to separate as drops from the body of ink, while allowing ink to be retained in non-selected nozzles, said drop selection apparatus being capable of producing said difference in meniscus position in the absence of said drop separation apparatus.
16. The invention defined in claim 12 wherein said print head comprises:
- (a) a plurality of drop-emitter nozzles;
- (b) a body of ink associated with said nozzles, said body of ink forming a meniscus with an air/ink interface at each nozzle and said ink exhibiting a surface tension decrease of at least 10 mN/m over a 30.degree. C. temperature range;
- (c) drop selection apparatus operable upon the air/ink interface to select predetermined nozzles and to generate a difference in meniscus position between ink in selected and non-selected nozzles; and
- (d) drop separation apparatus adapted to cause ink from selected nozzles to separate as drops from the body of ink, while allowing ink to be retained in non-selected nozzles.
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Type: Grant
Filed: Dec 3, 1996
Date of Patent: Sep 22, 1998
Assignee: Eastman Kodak Company (Rochester, NY)
Inventor: Kia Silverbrook (Leichhardt)
Primary Examiner: Jeffrey L. Sterrett
Attorney: Milton S. Sales
Application Number: 8/750,436